1. Field of Invention
This invention relates to a nuclear magnetic resonance (hereinafter called "NMR") imaging device, and, more particularly, to such a device capable of determining optimum scan parameters and of obtaining an original image from the scan parameters, thereby to obtain a calculated image for the relaxation times T1, T2 and the proton density .rho..
2. Description of Prior Art
A prominent feature of an NMR image resides in the image density being provided as a function of the nuclei density .rho. (which is typically, proton .sup.1 H density), relaxation times T1, T2, pulse sequences, and scan parameters such as RF pulse intervals, so that images of various contrasts can be obtained by varying the measuring parameters and hence a variety of information regarding diseases, for example, can be obtained.
However, this makes the comparison between clinical data difficult and interferes with the objectivity seen in the image.
In a known method of taking an image, pulse sequences or scan parameters of high image contrast with diseases to be examined, are experimentally selected. Furthermore, for those diseases lacking in clinical examples, a plurality of images are obtained by varying the image taking conditions. The image taking conditions are used to provide image contrast which correspond to experimentally determined diseases. However, such a method of accumulating clinical data is inefficient, and brings about significant practical problems in that scanning has to be made under various image taking conditions as occurs in actual clinical data cases. Also, it is nearly impossible for the scanning to be capable of obtaining an image of optimum contrast for a disease lacking in past clinical data.
There is also known a method of determining a calculated image for T1, T2 and .rho. through calculation from two or more images obtained by varying the condition of pulse application. However, since the method of evaluating the pulse sequence or scan parameter is not clear, when obtaining an original image for the calculated image of T1, T2, .rho., using this method, calculation for T1, T2, .rho. is not always performed under optimum conditions.
Another method has been used to obtain a pure calculated image for T1, T2, .rho. having an objective meaning for diagnosis through inter-image computation from a plurality of NMR images. However, since the calculated images for T1, T2, .rho. at present are poor in signal to noise (S/N) ratio, accuracy for the values of T1, T2, .rho. is not suitable for practical use.